Added a warning if an attempt is made to obtain a write lock twice from the same thread

HISTORY

@@ -9794,3 +9794,4 @@ Video Disk Recorder Revision History
   for recordings that are currently being edited.
 - Fixed a possible crash if an editing process is canceled while the edited
   recording is being replayed.
+- Added a warning if an attempt is made to obtain a write lock twice from the same thread.

thread.c

@@ -4,7 +4,7 @@
  * See the main source file 'vdr.c' for copyright information and
  * how to reach the author.
  *
- * $Id: thread.c 4.15 2020/09/16 13:48:33 kls Exp $
+ * $Id: thread.c 5.1 2022/11/13 15:25:52 kls Exp $
  */
 
 #include "thread.h"
@@ -753,6 +753,14 @@ bool cStateLock::Lock(cStateKey &StateKey, bool Write, int TimeoutMs)
      dbglocking("%5d %-12s %10p   timeout\n", cThread::ThreadId(), name, &StateKey);
      StateKey.timedOut = true;
      }
+  else if (threadId == cThread::ThreadId()) {
+     static bool DoubleWriteLockReported = false;
+     if (!DoubleWriteLockReported) {
+        dsyslog("WARNING: attempt to acquire write lock while already holding a write lock in the same thread - this may crash! (backtrace follows)");
+        cBackTrace::BackTrace();
+        DoubleWriteLockReported = true;
+        }
+     }
   return false;
 }